Electronic musical instrument having an attack circuit



Aug. 16, 1966 w ANDERSON ET AL 3,267,200

ELECTRONIC MUS ICAL INSTRUMENT HAVING AN ATTACK CIRCUIT Filed April 5.1963 000/0 5 sYaTEM m Volt/A16 c1200],

Kai/2, d I 30.691 3 AZ Q'fadaw' ATTOR EYS United States Patent 3,267,200ELECTRONIC MUSICAL INSTRUMENT HAVING AN ATTACK CIRCUIT Walter J.Anderson, Elgin, and Robert M. Grodinsky, Chicago, Ill., assignors toChicago Musical Instrument Co., Lincolnwood, 111., a corporation ofDelaware Filed Apr. 5, 1963, Ser. No. 270,999 Claims. (Cl. 84-126) Thisinvention relates generally to electronic musical instruments, and morespecifically to an attack circuit incorporated therein.

Although the principles of the present invention may be included invarious musical instruments, a particularly useful application is madein an electronic organ of the type having a number of voicing stops bywhich the organist may select the timbre of the music to be played. Byway of example, organ stops and associated circuits simulate variousorchestral instruments. The tones produced by such orchestralinstruments are further characterized by the rate at which the tone isproduced. By way of example, the various reed instruments require thatair be set into motion and the reed to be caused to vibrate before atone is produced. Similarly, a pipe organ pipe experiences a build-up ofair velocity before a useful tone of the desired volume is produced. Thesame is true for other reed instruments such as the oboe, and theaccordion. Collectively, such instruments have tones which, whilediffering intimbre, are similar in that each is produced with what ishere termed as a slow attac On the other hand, other instruments have asharp or fast attack, examples of which are the' trumpet and other brassinstruments, the piano, bells, chimes, and the like. A circuit forcontrolling the rate of attack of an electronic organic voice has beenpreviously included in the higher priced instruments, such inclusionbeing one reason for such instrument being initially higher priced.However, the mass organ market is in the lower priced instruments, inwhich it has not been practical for economic reasons to include suchfeature. In the past, a controlled attack circuit has been provided bymeans of a slow charging circuit composed of a large capacitor and arelatively small resistor. By changing the size of such resistor, therate at which the charge on the capacitor is developed has been varied.However, it has not been both convenient and economical to use a largecharging capacitor in combination with various sized resistors.Similarly, it has not been practical to use a small capacitor and largeresistance since such large resistance would lower the total voltageapplied from the keying circuit, and would further create a robbingsituation in response to the depressing of a number of keys when it wasdesired to produce a chord of tones.

The present invention contemplates the provision of a fast attack-slowattack circuit which employs no large charging capacitor, which does notcreate a robbing situation when a multiplicity of keys aresimultaneously played, and which employs no switch using a large numberof contacts for cutting in and out a multiplicity of keying resistors.The present invention is relatively simple in construction, and iseconomical to provide commercially.

Accordingly, it is an object of the present invention to provide animproved electronic musical instrument.

Another object of the present invention is to provide an electronicmusical instrument having an improved attack circuit incorporatedtherein.

A still further object of the present invention is to provide a novelslow attack circuit for an electronic musical instrument.

Patented August 16, 1966 Yet another object of the present invention isto provide a fast attack-slow attack circuit for an electronic musicalinstrument.

Many other advantages, features and additional objects of the presentinvention will become manifest to those versed in the art upon makingreference to the detailed description and the accompanying sheet ofdrawings in which a preferred structural embodiment incorporating theprinciples of the present invention is shown by way of illustrativeexample.

On the drawings:

The single figure is a schematic diagram representative of a portion ofan electronic musical instrument provided with an attack circuit inaccordance with the principles of the present invention.

As shown on the drawings:

The principles of this invention are particularly useful when embodiedin an electronic musical instrument, such as an organ, a representativeportion of which is illustrated on the drawing, generally indicated bythe numeral .10. The electronic instrument 10 includes a series ofgenerators 11, each of which comprises a signal source for one note.Depending upon the length of the keyboard of the instrument, there maybe as few as 36 and as many as 60 such generators. Each generator 11.maycomprise an oscillator, a divider stage, or other suitable source, andinclude an element, here illustrated as being an auxiliary plate 12which comprises a readout element which, when energized, iselectronically coupled to receive a, tone signal, such generators andreadout elements being known in the art. Each readout element 12 iscoupled by an output isolating resistor 13 'to a signal output bus 14leading to various voicing circuits 15 which are connected to an audiosystem 16. Normally the readout elements 12 send no signal from thegenerators 11, but when a coupling potential is applied thereto,individually, each individual readout element 12 having a couplingpotential will conduct a signal from the generator 11, through theoutput isolating resistor 13 and output bus 14 to the audio system 16.

Such coupling potential is obtained from a source of D.C.-potential 17,one side of which is grounded. The source of D.C.-couplin-g potential isa source of B-lvoltage, 300 volts D.C. being a typical value. The sourceof potential 17 is grounded at 18, and at its other side is connectedthrough a shuntable load resistor 19 to a keying bus 20. A playing-keyoperated switch 21 is provided for each signal source, one side orcontact 22 thereof being connected to the keying bus 20, and the otherside or contact 23 thereof being connected through a load resistor 24 tothe readout element 12. By the closing of any one of the key-switches21, a D.C.-coupling potential is thereby applied to the associatedreadout element 12 to effect playing of a note having that frequency. Innormal playing of the instrument, here referred to as fast attack, theload resistor 19 is shunted by means described below.

In accordance with the principles of the present invention, to provide aslow or delayed attack, a capacitor 25 is connected between one side orcontact 23 of each of the keying switches 21, and a pulse bus 26, commonto such capacitors 25. A further capacitor 27 is connected between thepulse bus 26 and ground and coacts with each of the capacitors 25 toserve therewith as a voltage divider having a tap or point with anintermediate voltage which is represented by the pulse bus 26. Each timethat one of the playing key-operated switches 21 is closed, not only isthe readout element 12 energized, but the capacitor means 25, 27 arealso charged, such charging causing a surge of potential or pulse toappear on the pulse bus 26.

Pulse bus 26 is connected to one side of a diode 28 which conducts suchpulse to an electronic switch 29.

The switch 29 is here illustrated as comprising a triode having a grid30 to which the pulse bus 26 is connected through the diode 28. Thetriode further includes a cathode 31 connected to a source of C-lorbiasing voltage 32 which is grounded. The triode includes a plate 33which, with the cathode 31, forms a plate circuit which is connected tothe keying bus 20, and hence across the load resistor 19.

A still further capacitor 34 is connected to the pulse bus 26, and morespecifically is connected to the grid 30 of the electronic switch 29. Ahigh resistance path to ground is provided from the grid 30, which pathincludes a resistor 35 which shunts the diode 28, and a resistor 36which shunts the capacitor 27. By the high resistance path 35, 36, thecharge on the capacitors shown herein will be leaked to groundprogressively.

The attack control portion of the circuit is under the selective andoperative control of a double-pole singlethrow switch 37 having onesection which includes a contactor 38 connected to the pulsing bus 26and a grounded contactor 39, and a second section having a pair ofcontactors 40, 41 connected in shunting or short-circuitin-g relation tothe load resistor 19.

During normal or fast attack playing of the instrument 10, the selectorswitch 37 will be in the closed position so that the load resistor 19 isshunted and so that the pulse bus 26 is grounded. During such normal orfast attack playing, any charge received by or pulse conducted by theattack softening capacitors 25 will be conducted directly to ground.Since the capacitors 25 are relatively small, they have only a slighttime-related elfect on the output tone. Owing to the rapid onslaught orinrush of the D.C.-coupling potential under this condition, a slightamount of thumping or popping may be experienced at the onset of theproduction of a tone. Any such thumping is eliminated by the provisionof a resistor 42 between the contactor 23 and a point between theresistor 24 and the capacitor 25 of each signal source 11.

When it is desired to employ a voicing stop of the type which shouldhave a slow attack, such as a reed stop, the attack control switch 37 isalso manually selectively actuated to the open position, as shown,thereby placing the attack control portion of the circuit in operativestandby relation.

During slow attack playing of the instrument 10, a closing of thekey-switch 21 also places the coupling potential across the capacitors25, 27 so that a pulse or voltage of intermediate value appears on thepulse bus 26 and is conducted unidirectionally by the diode 28 to thegrid 30. Since the electronic switchor triode 29 is normally biased tocut-01f, up to this point, no current has been flowing in the platecircuit. However, the presence of the pulse on the grid 30 renders theplate circuit thereof highly conductive, causing a relatively highcurrent to flow in the plate circuit which includes the load resistor19, thereby creating a substantial voltage drop thereacross, by whichthe coupling potential on the keying bus 20, from which the pulse wasderived, is immediately lowered so that the coupling potential on thereadout element 12 likewise is initially temporarily reduced. The pulseon the pulse bus 26 likewise charges the capacitor 34 which tends tomaintain the pulse voltage on the grid 30. While the grid voltage cannotleak reversely through the diode 28, the temporarily sustained gridvoltage or charge on the capacitor 34 can leak reversely through thehigh resistance path provided by the resistors 35, 36 to ground, therebygradually restoring the electronic switch to a nonconducting relationand simultaneously increasing the D.C.-coupling potential on the keyedreadout element 12. Thus the onslaught or attack of tone is regulated tosimulate the attack or slow build-up of a slow attack instrument, whileat the flick of a single switch, a rapid attack can be provided tosimulate the fast onslaught oftone or staccato required of otherorchestral voices.

In the fast attack position, the capacitors 25 achieve a slightsoftening of the attack, but this softening is of electronic switch 29is not conducting due to its bias voltage, the entire B+ voltage ispresent on the keying bus 20 to create the pulse when one of theswitches 21' is closed. However, such pulse immediately overcomes thecathode bias, causing the switch 29 to conduct heavily andinstantaneouslyrso that the coupling voltage likewise takes aninstantaneous heavy drop. The switch 29 may thereby be said to operatedegeneratively. Any pulse appearing on one of the capacitors 25 as aresult of keying, tends to reduce the level of voltage that is causingthe pulse, thereby slowing the build-up of the keyed tone.

The capacitor 27 serves to limit the maximum potential of the pulses onthe pulse bus 26 so that the pulse cannot be conducted by othercapacitors 25 to the readout elements 12 of non-played signal sources11, which might otherwise occur for an instant. Although the pulsevoltage is thereby reduced, it is still sufficiently large tocontrol theelectronic switch 29. The load resistor 19 not only serves as a load inthe plate circuit of the triode, but.

also tends to slow down the build-up of charge on the capacitors 25.

Typical values employed in the illustrated circuit are as follows:

Resistor 24 1 megohm. Resistor 13 1 megohm. Resistor 42 20,000 ohms.Resistor 36 22 megohms. Resistor 19 300,000 ohms. Resistor 35 5 megohms.Capacitor 25 .01 mfd. Capacitor 27 .01 mfd. Capacitor 34 .02 mfd. (seecomment below). Potential 17 300 volts D.C. Potential 32 5 volts D.C.Triode 29 12AX7.

The attack control tube or triode 29 is of the high-mu triode type, andother specific values identified are appropriate to the identified tube.

The time constant of the resistors 35, 36 and capacitor 34 is adjustedso that the grid 30 of the tube 29 returns to cut-off and restores fullfiring potential in a period of time which is short compared to thelength of time during which a note is held. This produces a slowbuild-up of the tone or slow attack. Yet the duration of build-up isshort enough so that voltage is restored and the process repeated forsubsequent notes played in rapid order.

Although various minor modifications might be suggested by those versedin the art, it should be understood that we wish to embody withinthescope of the patent warranted hereon all such embodiments asreasonably and properly come within the scope of our contribution to theart.

What we claim is:

1. An attack circuit for an electronic musical instrument including aseries of signal sources having readout elements connected to a commonoutput bus, and a series of key switches operative to apply a couplingpotential on the readout elements, said circuit comprising:

(a) a pulse bus having capacitative connections with the readoutelements; and

(-b) a triode having a grid connected to said pulse bus,

and a normally non-conducting plate circuit under the control of saidgrid, said plate circuit being connected across the source of couplingpotential.

2. An electronic musical instrument, including in combination:

(a) a series of signal sources having readout elements;

(b) an output bus connected to said readout elements;

(c) a source of D.C.-coupling potential;

(d) a series of key-switches operative when closed to apply the couplingpotential to the readout elements to couple the signals to the outputbus;

(e) a pulse bus having capacitive means connecting said pulse bus withsaid readout elements and thus momentarily energized therewith byclosing of any of said key-switches; and

(f) a triode having a grid connected to said pulse bus, and a normallynon-conducting plate circuit means connected across said source ofD.C.-coupling potential, said plate circuit means in response to a pulseon said grid being conductive to momentarily lower the couplingpotential.

3. In an electronic musical instrument having a series of signal sourceseach including an electron-coupled readout element, an output busconnected to said readout elements, a source of D.C.-coupling potential,and a series of key-operated switches each having one side connected tosaid source of potential, and the other side connected to one of saidreadout elements respectively, the improvement in combination therewith,comprising:

(a) a pulse bus;

(-b) a capacitor for each of said switches and connecting said otherside thereof to said pulse bus; and

(c) a normally non-conducting electronic switch connected to said pulsebus and being highly conductive in response to any signal on said pulsebus, said switch being connected to said source of potential by suchmeans .as to be operative, when conductive, to impress a load on saidsource of potential, thereby transiently reducing its effectiveness ineffecting coupling of said readout elements.

4. In an electronic musical instrument having a series of signal sourceseach including an electron-coupled readout element, an output busconnected to said readout elements, a source of D.C.-coupling potential,and a series of key-operated switches each having one side connected tosaid source of potential, and the other side connected to one of saidreadout elements respectively, the improvement in combination therewith,comprising:

(a) capacitative voltage divider means connected to said other side ofsaid switches, and having an electrically common intermediate voltagetap; and

(b) a normally non-conducting electronic switch connected to saidvoltage tap and being highly conductive in response to any signal onsaid voltage tap, said switch being connected to said source ofpotential by such means as to be operative, when conductive, to impressa load on said source of potential, thereby transiently reducing itseffectiveness in effecting coupling of said readout elements.

5. In an electronic musical instrument having a series of signal sourceseach including an electron-coupled readout element, an output busconnected to said readout elements, a source of D.C.-coupling potential,and a series of key-operated switches each having one side connected tosaid source of potential, and the other side connected to one of saidreadout elements respectively, the improvement in combination therewith,comprising:

(a) a pulse bus;

(b) a capacitor for each'of said switches and connecting said otherside'thereof to said pulse bus;

(0) a further capacitor connected between said pulse bus and ground;

(d) a triode having a cathode, having a grid connected to said pulsebus, and having a plate connected to said one side of said switches andin circuit with a load to said source of potential; and

(e) means connected to said cathode and normally biasing said cathode tocut-off.

6. In an electronic musical instrument having a series of signal sourceseach including an electron-coupled readout element, an output busconnected to said readout elements, a source of D.C.-coupling potential,and a series of key-operated switches each having one side connected tosaid source of potential, and the other side connected to one of saidreadout elements respectively, the improvement in combination therewith,comprising:

(a) a pulse bus;

(b) a capacitor for each of said switches and connecting said other sidethereof to said pulse bus;

(c) a diode connected to said pulse bus to conduct pulses receivedtherefrom; and

(d) a triode having a grid connected to receive pulses from said diode,and a normally non-conductive plate circuit controlled by any pulse onsaid grid, said plate circuit being connected to said source ofpotential and comprising means to load said source of potential to lowerits voltage momentarily.

7. In an electronic musical instrument having a series of signal sourceseach including an electron-coupled readout element, an output busconnected to said readout elements, a source of D.C.-coupling potential,and a series of key-operated switches each having one side connected tosaid source of potential, and the other side connected to one of saidreadout elements respectively, the improvement in combination therewith,comprising:

(a) a pulse bus;

(b) a capacitor for each of said switches and connecting said other sidethereof to said pulse bus;

(0) a diode connected to said pulse bus to conduct pulses receivedtherefrom;

(d) a triode having a grid connected to receive pulses from said diode,and a normally non-conductive plate circuit controlled by any pulse onsaid grid, said plate circuit being connected to said source ofpotential and comprising means to load said source of potential to lowerits voltage momentarily; and

(e) a further capacitor so connected to one side of said diode as toenable it to be charged by any pulse received by said pulse bus, saidcapacitor being of such size as to lengthen the duration of said pulseon said grid.

8. In an electronic musical instrument having a series of signal sourceseach including an electron-coupled readout element, an output busconnected to said readout elements, a source of D.C.-cou-plir1gpotential, and a series of key-operated switches each having one sideconnected to said source of potential, and the other side connected toone of said readout elements respectively, the improvement incombination therewith, comprising:

(a) a pulse bus;

(b) a capacitor for each of said switches and connecting said other sidethereof to said pulse bus;

(c) a diode connected to said pulse bus to conduct pulses receivedtherefrom;

(d) a triode having a grid connected to receive pulses from said diode,and a normally non-conductive plate circuit controlled by any pulse onsaid grid, said plate circuit being connected to said source ofpotential and comprising means to load said source of potential to lowerits voltage momentarily;

(e) a further capacitor connected to said grid for maintaining saidpulse on said grid; and

(f) a high resistance leakage path connected to said grid fordischarging said further capacitor.

' 9. In an electronic musical instrument having a series of signalsources each including an electron-coupled readout element, an outputbus connected to said readout elements, a source of D.C.-couplingpotential, and a series of key-operated switches each having one sideconnected through a load to said source of potential, and the other sideconnected to one of said readout elements respectively, the improvementin combination therewith, comprising:

(a) a pulse bus;

(b) a capacitor for each of said switches and connecting said other sidethereof to said pulse bus;

(c) a normally non-conducting electronic switch connected to said pulsebus and being highly conductive in response to any signal on said pulsebus, said 7. switch being connected to said load by such means as to beoperative, when conductive, to increase the voltage drop across saidload, thereby transiently reducing the effectiveness of said source ofpotential in effecting coupling of said readout elements; and

(d) switch means for selectively simultaneously shunting said load andgrounding said pulse bus.

10. In an electronic musical instrument having a series of signalsources each including an electron-coupled readout element, an outputbus connected to said readout elements, a source of D.C.-couplingpotential, and a series of key-operated switches each having one sideconnected to said source of potential, and the other side connected toone of said readout elements respectively, the improvement incombination therewith, comprising:

(a) a pulse bus;

(b) a capacitor for each of said switches and connecting said other sidethereof to said pulse bus;

() a normally non-conducting electronic switch connected to said pulsebus and being highly conductive in response to any signal on said pulsebus, said switch being connected to said source of potential by suchmeans as to be operative, when conductive, to impress a load on saidsource of potential, thereby transiently reducing its effectiveness ineffecting coupling of said readout elements; and

(d) switch means for selectively preventing any pulse on said pulse busfrom reaching said electronic switch.

11. In an electronic musical instrument having a series of signalsources each including an electron-coupled readout element, an outputbus connected to said readout elements, a source of D.C.-cou-plingpotential, and a series of key-operated switches each having one sideconnected through a load to said source of potential, and the other sideconnected to one of said readout elements respectively, the improvementin combination therewith, comprising:

(a) a pulse bus;

(b) a capacitor for each of said switches and connecting said other sidethereof to said pulse bus;

(c') a further capacitor connected between said pulse bus and ground;

(d) a diode connected to said pulse bus to conduct pulses receivedtherefrom;

(e) a triode having a cathode, having a grid connected to said. pulsebus, and having a plate connected to said one side of said switches, andin circuit with said load to said source of potential;

(f) means connected to said cathode and normally biasing said cathode tocut-off;

(g) a still further capacitor connected to said grid for maintainingsaid pulse on said grid;

('11) a high resistance leakage path connected to said grid fordischarging said further capacitors; and

(i) switch means for selectively simultaneously shunting said load andgrounding said pulse bus.

12. In an electronic musical instrument having a series of signalsources each including an electron-coupled readout element, an outputbus connected to said readout elements, a source of D.C.-couplingpotential, and a series of key-operated switches each having one sideconnected to said source of potential, and the other side connected toone of said readout elements respectively, the improvement incombination therewith, comprising:

(a) means producing a surge of a direct current of momentary duration inresponse to each activation of each of said key-operated switches; and

(b) means responsive to each such momentary surge and operative to delaybuild-up of said coupling potential on the associated readout element.

13. In an electronic musical instrument having a series of signalsources each including an electron-coupled readout element, an outputbus connected to said readout elements, a source of D.C.-couplingpotential, and a series I of key-operated switches each having one side.connected to said source of potential, and the other side connected toone of said readout elements respectively, the improvement incombination therewith, comprising:

(a) an attack control tube normally biased to cut 0E and having a platecircuit means connected across said source of potential and operative todecrease the D.C.-coup1ing potential when conductive; and

(b) a series of capacitors connected between said other sides of saidswitches and the grid of said tube for applying keyed potential pulsesto said grid to thereby render said tube conductive in response to eachpulse.

14. In an electronic musical instrument having a series of signalsources each including an electron-coupled readout element, an outputbus connected to said readout elements, a source of D.C.-couplingpotential, and a series of key-operated switches each having one sideconnected to said source of potential, and the other side connected toone of said readout elements respectively, the improvement incombination therewith, comprising:

(a) a normally non-conducting attack-control electronic switch forming apart of a load circuit means connected across said source of potentialand, said load circuit means being operative to decrease the DC.-coupling potential when said electronic switch is conductive; and

(b) a series of capacitors connected between said other sides of saidkey-operated switches and a control element of said electronic switchfor applying potential pulses thereto under the control of saidkey-operated switches to thereby render said electronic switchmomentarily conductive in response to each pulse.

15. In an electronic musical instrument having a series of signalsources each including an electron-coupled readout element, an outputbus connected to said readout elements, a source of D.C.-couplingpotential, and a series of key-operated switches each having one sideconnected to said source of potential, and the other side connected toone of said readout elements respectively, the improve ment incombination therewith, comprising:

(a) a load resistor connected in series between said source ofD.C.-coupling potential and said one side of said key-operated switches;and

(b) means, connected across said load resistor, and

operative in response to closing of any of said keyoperated switches, toproduce a substantially instantaneous increase in voltage dropthereacross which drop progressively decreases.

References Cited by the Examiner UNITED STATES PATENTS 2,227,068 12/1940 Curtis.

2,483,823 10/1949 George 841.26 3,038,365 6/1962 Peterson 841.26

ARTHUR GAUSS, Primary Examiner. I. Q. EDELL, Assistant Examiner.

1. AN ATTACK CIRCUIT FOR AN ELECTRONIC MUSICAL INSTRUMENT INCLUDING A SERIES OF SIGNAL SOURCES HAVING READOUT ELEMENTS CONNECTED TO A COMMON OUTPUT BUS, AND A SERIES ON KEY SWITCHES OPERATIVE TO APPLY A COUPLING POTENTIAL ON THE READOUT ELEMENTS, SAID CIRCUIT COMPRISING: (A) A PULSE BUS HAVING CAPACITIVE CONNECTIONS WITH THE READOUT ELEMENTS; AND AND A NORMALLY NON-CONDUCTING PLATE CIRCUIT UNDER THE CONTROL OF SAID GRID, SAID PLATE CIRCUIT BEING CONNECTED ACROSS THE SOURCE OF COUPLING POTENTIAL. 